In the related art, a lithium secondary battery is typically manufactured by using a separator as an insulator between a strip-like positive plate and a negative plate, winding the electrode stack spirally to constitute an electrode assembly (or a jelly roll), accommodating the electrode assembly in a shell, and then mounting a cap assembly provided with electrode terminals to the shell. Commonly known prismatic lithium secondary batteries comprise collector plates for collecting a great amount of current within a short time with respect to capacity or output, as shown in FIG. 8. The collector plates are leaded out at both sides of the electrode assembly and extend facing the cap assembly.
To suppress occurrence of a short circuit, it is proposed in the related art to suppress battery overheating due to an internal short circuit by applying a ceramic composite material layer containing inorganic fillers and matrix materials (i.e., binders) on a microporous film layer of a composite separation film.
As the electrode assembly uses the composite separation film having the ceramic composite material layer, the electrode assembly may be thickened, leading to a reduction in volumetric energy density of the lithium secondary battery. When the battery is charged and discharged repeatedly, the electrode plates may expand and shrink significantly and produce a large amount of gas, thereby resulting in deformation of the electrode assembly. The ceramic composite material layer bonded via the binder may come loose due to the expansion and thus be damaged and fall off from the microporous film. Thus, the function of the ceramic composite material layer to suppress battery overheating due to internal short circuit is affected, and the safety performance of the battery is also greatly affected.